At the start of the Second World War, a little known aircraft designer came up with the idea of some new bombs. They were to change the fortunes of the British war effort. Barnes Wallis is most famous for his Dambuster bomb, used with great effect in 1943, and immortalized in the film of the same name, but he also designed three other bombs, the biggest of which was Grand Slam, a huge 'earthquake' bomb used to great effect against U-boat pens and other difficult targets in occupied Europe. This is the fascinating story of the man, his bombs, the trials of getting them in to service and the story of their effective use against the Nazis.